1. Field of the Invention
The invention relates generally to a hydromechanical drive assembly, and more particularly to a hydromechanical drive assembly having a hydrostatic swash-plate type axial piston motor and a mechanical transmission located downstream of the axial piston. The transmission has a driven shaft and the axis of rotation of the driven shaft is coaxial with the axis of rotation of the cylindrical drum of the axial piston motor.
2. Description of Related Prior Art
United Kingdom Patent No. 1,391,006 discloses such a hydromechanical drive assembly wherein the torque of the axial piston motor is not transmitted to its shaft as in the conventional manner. Instead, the torque is transmitted to teeth on the outside diameter of the cylindrical drum which transmit it through the web of a planetary gear to a transmission-side driven shaft. The shaft of the axial piston motor is connected to the housing so that it cannot rotate and serves as a bearing for the cylindrical drum and absorbs reaction forces of the work pistons. The design of the drive assembly of the aforementioned United Kingdom patent includes many individual parts, resulting in high fabrication and installation costs. Furthermore, the scope of the application of the drive assembly is restricted to a hub drive for single-wheel vehicles. Additionally, the drive assembly is not well suited for applications in which high lateral forces affect the transmission-side driven shaft, such as when driving the slewing gear of an excavator, because the space between the two bearings for the driven shaft is small.